Point contact fuse



Jan. 9, 1951 H. H. PORTER 2,537,855

POINT CONTACT FUSE Filed June 9, 1944 /0 3/ '1 30 I I' 3 k H 6 i /6 32 34 HI 2 'I I 2 l. w g: 45 43 i, 4 I9 40 4 43 gnaw M HenryHfurtEr' gas? a Maw/262M We Patented Jan. 9, 1951 UNITED STATES DFFlCE POINT CONTACT FUSE Henry H. Porter, Silver Spring, Md. assignor to the United States of America as represented by the Secretary of War 2 Claims. i

This invention relates to point contact fuzes for projectiles, more particularly, of the type employing a primer rotor which is normally in disarmed position relative to the firing pin and turned toarmed position after the projectile has left .the gun. Oneof the objects of the invention is toprovide a safety detent for the primer motor which. will positively hold the rotor in disarmed position and which coacts with the firing pin to accomplish this purpose. this and such other objects of invention as may herein appear or be pointed out I have shown one embodiment of my invention in the accompanying drawing, wherein:

Figure 1 is a sectional elevation of the improved fuze in normal, disarmed position;

Figure 2 is a cross-sectional plan taken on the line.22 of Figure 1;

Figure.3 is asectional elevation similar to Figure 1 but showing the parts as they appear during set-back as the projectile traverses the gun barrel, .the rotor still remaining in disarmed position; and

Figure 4 is a similar sectional elevation showing the parts in armed position, after the projectile has left the gun.

The body or nose I of the improved point contact fuze has a central cylindrical passage 3 in communication with an enlarged mouth 2 at the tip of the fuze and with an internal chamber 4 eccentrically disposed relatively to the longitiudinalaxis of the fuze and the central passage 3. Nose'or body .1 is reduced at its lower end to provide an externally threaded base portion 5.

Formed in the base portion 5 is a substantially hemispherical recess 6 which is normally closed by a disc -1 held in an annular groove 8 formed in the lower rim of the base portion. Between the top of thehemispherical recess 6 and the said internalchamber 4 is a central bore 9. The hemispherical recess 6, which constitutes the booster, and the central bore 9, which constitutes the relayrare filled with an explosive compound.

Slidably mounted within the central passage 3 is .a firing pin-generally designated as It] and provided at its lower end with a head i l in sliding contact with the wall of cylindrical passage 3; depending from head I l is tapered pin l2. At its upperend the firing pin is provided with a flange l3 which is slidably received in the enlar ed mouth 2.; pro ecting forwardly from flange I3 is button l4 whic'his adapted .to contact the target. Outward displacement of the firing pin is prevented by an in-turned annular flange la provided at the upper end of the nose. A compress For the attainment of 1' 2 sion coil spring Eli is interposed between the annular shoulder at the bottom of enlarged mouth 2 and the E3 of the firing pin.

Centrally located in the internal chamber 4 is a spindle 21, see Figures 1 and 2, about which is pivotally mounted a rotor 20. It will be noted, best from Figure 2, that spindle 2| is not positioned at the center of gravity of rotor 20 but at a point eccentric thereto. A primer 22 is placed in a vertical bore A, see Figures 2 and 4, which extends through the rotor. When the eccentric rotor 2% is in armed position, as in Figures 2 and 4, primer 22 is alined with the central axis of the fuze, and also with the firing pin which is located longitudinally thereat, as already described. For the purpose of maintaining rotor 26 in disarmed position its upper surface is provided with a detent cup or depression 23 in which is received taper pin 92 of the firing pin preventing turning of the rotor on its spindle 2 i. It will be observed from Figure 2 that detent cup 23 and primer 22 are located at the same radial distance from the spindle 2! so that the detent cup 23 may be aligned with the firing pin (at the central axis A of the fuze) in the disarmed position of the rotor, in armed position as shown in Figure 3, or the primer 22 may be aligned with the firing pin, as

Figures 2 and 4.

Compres ion spring l5 tends to move the firing pin upwar .ly and thus to Withdraw its taper pin i2 from detent cup 23. To normally prevent this upward movement of the firing pin, the upper annular shoulder formed at the junction of head ll and the stem of the firing pin is recessed to define an annular groove 16 and an annular lip ll. Cooperative with the firing pin, and more part cularly with the said annular groove l6 and annular lip I '1 thereof, are a pluralitytwo, as shcwnof detent units designated generally as 3). The detent units 30 are placed in lateral bores lb radially disposed in nose body I between central longitudinal bore 3 and the outside surface of the nose. Each detent unit 30 comprises a casing 3| securely positioned within radial bore lb and provided with a central opening 32 facing central bore 3. Slidably mounted within casing I I is a thimble 33 havim a stem 34 clearing through central opening 32 and provided at its end with a fiance 35 beveled to be received within the annular groove of the firing pin. A compression coil spring 36 between thimble 33 and the outer end of casing 3| urges the thimble towards t e firing pin with the flange 35 in springpressed relation thereto.

In the normal position of the parts, shown in Figure 1, the beveled flanges 35 of the detents are received in the annular groove I6 of the firing pin to hold the pin from being moved upwardly by the compressed coil spring I5. In this restrained position of the firing pin its taper pin i2 is received in the detent cup 23 of the primer rotor 20 to hold the rotor in disarmed position.

When the gun is fired, set-back created by the explosion of the propellant charge and acting,

during acceleration, upon the projectile as it traverses the gun barrel, will move the firing pin Ill downwardly to the position shown in Figure 3, further compressing spring I5. As the firing pin moves downwardly, under the influence of set-back, its taper pin I2 is fully received in detent cup 23 of the rotor. For this reason detent cup 23 is somewhat deeper than the length of taper pin I2 and its diameter is somewhat greater than the base diameter of the taper pin. In moving downwardly the annular groove l6 and annular lip I! become free of the beveled flanges of the detent units 30, as shown in Figure 3. Also as shown in Figure 3 the compression springs 36 of the detent units continue to press the beveled flanges 35 against the stem of the firing pin. Thus, in unarmed condition, the nib or point I2 of the firing pin remains in its socket 23, to prevent the rotor or cage 20 from swinging on its pivot point 2 I, until the projectile has passed out of the gun-barrel.

As soon as the projectile encounters the riding of the gun barrel and begins to rotate or spin about its longitudinal axis, centrifugal force, which acts upon the detent units 39, tends to cause them to move outwardly, against their springs 36. However, the centrifugal force required to withdraw the detents does not become effective until the projectile has moved approximately to the muzzle-end of the gun. By the time such a point is reached, the force of setback in the projectile has decreased to a degree where it is practically ineffective. On the other hand, the centrifugal force has developed sufficiently to withdraw the detents, and they move outwardly as described. In the outward position of the detents, shown in Figure 4, their beveled flanges 35 are somewhat beyond the head H of the firing pin and therefore out of the path of annular groove l6 and are ineffective to prevent forward movement of the firing pin.

As acceleration of the projectile dimishes, the eiTect of set-back disappears and the spring I5, originally under compression (Figure 1) and given added compression by set-back (Figure 3), moves the firing pin forwardly, to the forward position shown in Figure 4. This forward movement of the firing pin is aided by creep as the projectile begins to decelerate. It should be noted that centrifugal force due to the spinning of the projectile is still active at this time to main tain the beveled flanges 35 of the detents out of the path of annular groove I6 of the firing pin, as in Figure 4, so that the firing pin may move to forward position, as shown'in Figure 4; But after the firing pin has moved to forward position it becomes impossible for the beveled flanges 35 to engage in the annular groove |6 of the fir;- ing pin head II inasmuch as the beveled flanges are now in contact with the outer surface of head II, as shown in Figure 4.

' As the firing pin moves to forward position its taper pin I2 is withdrawn from detent cup 23, so that rotor 20 becomes free to turn on its spindle 2|. Centrifugal force of the spinning projectile turns the eccentrically-mounted mm! 29 to armed position with primer 22 on the longitudinal axis in alignment with taper pin I2 of the firing pin and relay 9 of the booster charge. The rotor remains in armed position until contact button I4 in striking the target forces the firing pin downward to cause its taper pin I2 to detonate primer 22. p I

A supplementary detent 40 may be provided to retain the rotor in disarmed position until acted upon by centrifugal force to free the rotor.

Supplementary detent 40 has a casing 4| secured in radial bore Ic and provided with an opening 42 through which clears a pin projecting from a thimble 43 slidably mounted in casing 4|. Detent pin 451s received in a detent cup I9 provided in rotor 20. A compression coil spring 46 between thimble 43 and the end wall of casing 4| presses detent pin 45 in detent cup I9 to maintain the rotor 2a in disarmed position. When the projectile is fired, centrifugal force withdraws pin 45 of supplementary detent 40 from detent cup I9,,as shown. in Figure 4.

It was pointed out above that the diameter of detent cup 23 is somewhat larger than the diameter at the base of the taper pin I2, so that the pin may be received within cup 23, as in Figure 3. Because of this circumstance there will be some free play or looseness betweenthe detent cup 23 and the taper pin I2 when the firing pin is in normal position, as in Figure 1. This freedom of rotor 28 to turn a limited angular extent on its spindle 2| is not objectionable but may be entirely overcome by making a snug fit between pin 45 and cup It of the supplementary detent 40.

I claim:

1. In a point contact fuze, the combination of a fuze body, a rotor having an eccentrically disposed pivotal axis mounted at a predetermined distance from the central axis ofthe fuze body and a primer positioned the-said predetermined distance from the pivoted axis whereby in the armed position of the rotor the primer will be at the central axis of'the fuze body, a firing pin slidably mounted on the central axis of the fuze body, the said rotor having a first cup positioned the said predetermined distance from its said pivotal axis whereby in the disarmed position of the rotor the said first cup will be at the central axis to receive the end of the said firing pin, a spring urging the firing pin forward to withdraw its. said end from the said first cup, a plurality of detent members disposed radially to the firing pin, each having a beveled flange at their inner ends and a compression spring urging their said beveled flanges in contact with the firing pin, the firing pin having an annular groove beveled to receive the said beveled flange of the detent members to hold the firing pin against forward movement by its said spring withits end received in the said first cup to maintain the rotor in disarrred position, additional rotor locking means disposed.v at right angles to the axis of the said firing pin arranged to retain the said, rotor in disarmed position until acted upon by centrifugal force to free said rotor, said locking means comprising a spring urged pin receivable. in a second cup in said rotor the said firing pin being moved rearwardly by set-back upon gun firing to withdraw its said annular groove from engagement with the beveled flanges of the detent members, said beveled flanges engaging the stem of said firing pin forward of said annular groove after setback; the detent members then moving outwardly by centrifugal force of the spinning projectile to position its dis-engaged beveled fianges beyond the said annular groove of the firing pin whereby the firing pin may move forwardly under impulsion of its said compressed spring and creep of the decelerated projectile, to withdraw its end from the said first cup to free the rotor for turning by the said centrifugal force to armed position, the firing pin being moved rearwardly by impact with the target to detonate the primer of the armed rotor.

2. In a point contact fuze, the combination of a fuze body, a rotor having an eccentrically disposed pivotal axis mounted at a predetermined distance from the central axis of the fuze body and a primer positioned the said predetermined distance from the pivotal axis whereby in the armed position of the rotor the primer will be at the central axis of the fuze body, a firing pin slidably mounted on the central axis of the fuze body, the said rotor having a first cup positioned the said predetermined distance from its said pivotal axis whereby in the disarmed position of the rotor the said first cup will be at the central axis to receive the end of the said firing pin, additional rotor locking means disposed at right angles to the axis of said firing pin arranged to retain the said rotor in disarmed position until acted upon by centrifugal force to free said rotor, said locking means comprising a spring urged pin receivable in a second cup in said rotor a spring urging the firing pin forwardly to withdraw its said end from the said first cup, a plurality of detent members having beveled flanges disposed radially to the firing pin and spring pressed towards the firing pin, the firing pin, the firing pin having a beveled annular groove cooperating with the said beveled fianges to hold the firing pin against forward movement by its said spring with its end received in the said first cup to maintain the rotor in disarmed position, the said beveled flanges being dis-engaged from the detent members by rearward movement of the firing pin upon set-back, the detent members moving outwardly by centrifugal force of the spinning projectile beyond the said holding means of the firing pin whereby the firing pin may move forwardly under impulsion of its said compressed spring and creep of the decelerated projectile, to withdraw its end from 7 y the said'first cup.

HENRY H. PORTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,014,393 Mathsen Sept. 17, 1935 2,129,692 Hottinger Sept. 13, 1938 2,231,581 Junghans Feb. 11, 1941 FOREIGN PATENTS Number Country Date 299,668 Germany July 18, 1919 257,335 Great Britain Aug. 27, 1926 

